SV: Re: SV: Re: [sdiy] Compensating PTC and NTC resistors

Amos controlvoltage at gmail.com
Wed Mar 19 17:50:25 CET 2008


>> Any non-trivial circuit will be difficult to understand the *complete*
>> picture. That's why we make approximations.  The temp.co resistor is just
>> one such approximation.  It gets us "close enough" to perfection at minimal
>> cost.
>
>Approximations are not always a neat solution to a problem.
>Making approximations on saftey critically systems are dangerous
>engineering behavior.Close enough are no cigar.

There is nothing wrong with either of these statements, but I question
their relation to each other.  Specifically, if you are designing
critical safety systems whose success/failure depends upon knowing the
exact TC of the carbon resistors, maybe your design isn't safe enough.
 In that case, I assume that an approximation would be used to
estimate the "absolute worst possible case" of temperature drift, to
be sure that your design could not be negatively affected by this
parameter.

I apologise for not contributing usefully to this discussion.

-Amos



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